Impact of Rendering on Drying Stage of Light Earth Walls

Light earth is a material made of vegetal aggregates (such as hemp shives) and earth acting as a binder. During the manufacturing process, water is added to create a mixture with a good rheology for spraying. The amount of water should be sufficient to account for the absorption of the aggregates. Once the material is manufactured, the excess water should be evacuated through drying before applying renders to its surface. This study focuses on the drying of three wall-scale systems (with dimensions of 22 × 88 × 97 cm) manufactured using the spraying process. The temperature and relative humidities were monitored at different positions of the walls, while the mean moisture content was evaluated on a separated sample (with dimensions of 8.5 × 30 × 30 cm). In addition, there were some attempts to measure the surface moisture content with some commercially available devices. After 3 months, an earth-based render was applied to one wall, allowing the investigation of the influence of rendering on the hygrothermal behavior of walls during the drying stage. The experimental results were compared to hygrothermal simulations. The validated model was then used to predict the drying of the light earth wall under different scenarios.